Calculating the cost of product precisely and presenting reliable information and reports for economic decision making are the objectives of cost accounting systems. But, the independent auditors reports reveal that most of the manufacturing companies, especially state companies, do not possess suitable methods for cost accounting of products. To identify the insuficiencies of cost accounting systems of these companies, two companies, involved in steel industry were selected and operation process as well as working methods of their different part were examined. The results show that the cost accounting system of the selected companies, compared to a suitable accounting system is very in appropriate. The reasons of its inappropriateness are absence of proper procedures for production cercufation, absence of accounts related to production process, absence of correct information a bout the capacity of production lines, inability to recognize costs behavior, not using proper bases for over head allocations, not using budget mechanism related to list of the bills, not colwlating and registering variances and not preparing reliable managerial reports at certain periods of time.